As I don't know the story, I can't tell for sure. But likely, the slave girl herself is a main character.
Not having read the'slave girl pt 3 story', it's impossible to accurately name the main characters. But in a story about a slave girl, there could be other slaves who play important roles, either as friends or comrades. There may also be antagonists such as cruel overseers or those who uphold the system of slavery, in addition to the central figure of the slave girl.
Perhaps there is a fellow slave or a sympathetic free person in the novel. This character could play an important role in the slave girl's journey, either by providing support, friendship, or a different perspective on her situation.
Since I don't know the exact'school slave story', it could be students who are the main characters. They might be the ones facing the difficult situations that make them feel like slaves.
There are the king, who is likely in a position of great luxury and control, and the slave, who is probably at the bottom of the social hierarchy. These two characters are central to the story as their relationship, whether it's one of conflict, friendship, or mutual growth, drives the plot forward.
The slave girl herself is of course the most important character. She is the one whose experiences and emotions are being told through the letters. There might also be her master or mistress as important characters, as they play a role in her life as oppressors. And perhaps there are other slaves in the story who are part of her community and support system.
The main characters are the slave and the lion.
As I don't know the details of this 'full time slave story', I can't say for sure who the main characters are. It could be the slaves themselves, their masters, or perhaps other people related to the slave system like overseers or abolitionists.
In slave boy stories, the central character is, of course, the slave boy. He experiences the brutality and unfairness of slavery first - hand. There might also be a slave master's son or daughter. Their relationship with the slave boy can be complex, ranging from friendship to further exploitation. Another main character could be a runaway slave who serves as an inspiration for the slave boy. This runaway slave has tasted freedom and might encourage the boy to strive for the same.
Since I haven't read 'slave to the darkness novel', I can only speculate. There could be a protagonist who is forced into this state of being a slave to darkness. Maybe there is a mentor - like figure who tries to help the main character break free, or there could be other characters who are also trapped in the same situation and they bond over their shared plight.
Since I haven't read the 'slave to darkness novel', it's hard to say for sure. However, the main characters might include a protagonist who is on a path to self - discovery while being a slave to darkness. There could also be an antagonist representing the pure essence of the dark power that controls the slaves. And perhaps there are other supporting characters who are either fellow slaves or those trying to free the slaves from the clutches of darkness.
Obviously, the boy slave himself is one of the main characters. He is the central figure around whom the story revolves. There may also be the slave master, who represents the oppressive force in the boy's life.